observe-call
Writes a single ledger row for the most recent tool-use call: reads the API response's usage field (authoritative), looks up the model rate in shared/rate-card.json, applies prompt-cache modifiers (1.25× write, 0.1× read), computes billed cost, and appends to plugins/cost-tracker/state/ledger-YYYY-MM.jsonl. Use when: a PostToolUse hook fires for any tool and attribution metadata is available via ENCHANTED_ATTRIBUTION env. Do not use for forecasting (see /pech-forecast → forecast-cost) or for anomaly detection (see budget-watcher/detect-anomaly).